The meaning of Truth according to Tatha sutta in SN commentary gives the explanation of actual (tatha), unerring (avitatha) and not otherwise (anaññatha). The four noble truths are “actual (tatha) in the sense of not departing from the real nature of things.” Such is the nature of suffering, the respective suffering also should be eradicated with respective factor and for eradication of the respective suffering needed for the respective factor which does not change to another factor so it is called the nature. It does not change the true nature of things. And also just as for the relieving fever we should take ingredient of Paracitamol of allopathic medicine or other constituent of quinine ingredient but beyond those ingredient medicines (of allopathic medicine) will not work for relieving the fever. (In actual it may not be but only to show the relevant simile of the word “actual”). And also for the eradicating the sceptical doubt and wrong-view one should attain the first path wisdom. Otherwise one cannot totally eradicate Sceptical doubt (Vicikiccha) and wrong-view (ditthi). So it is to be only eradicated by sottapatti magga person not by other person. This is called the nature of the world that certain things should be only accomplished with certain thing not with other things. And also just as we feel hungry, the hunger should be relieved by eating food not by other thing more than food. This is called the actual of not departing from the real nature of things how it is to be understood. And also it will clear regarding the suppression of the respective Jhàna factors that suppress to the respective hindrances (nivàraäa). And it is not to be suppressed by other factors. As it had discussed about the truth are not from the ultimate aspect but it is just from the conventional aspect. For example in the ultimate aspect the five jhàna factors has related with other mental state and consciousness by means of Conditional relation method. In this case the simile had take form the convectional aspect.
“For the suffering (truth) is stated to be just suffering (not more than that i.e. the cause, cessation and the path truth). And the word unerring is because of non-falsification of its real nature for suffering does not become non-suffering. Not otherwise, is because of not arriving at a different nature; for suffering does not arrive at the nature of origin (of suffering etc.) The rests truths also should be understood in the same way and the word not otherwise (anaññatha). In the simpler and more straightforward sense that the truths are ‘not otherwise’ than the way things really are” It means that suffering is only suffering it is neither the cause, nor the path etc.
1. Samyutta Nikaya- III, Yangon: Ministry of Religious Affairs p-329 (refers to Myanmar Pali Tipitaka version) or SN-Vol-II,p 1963